The present disclosure relates to a power amplification module. There is a demand for mobile communication terminals such as cellular phones to be able to support a plurality of communication systems (multi-mode) and a plurality of frequency bands (multi-band) as a single terminal. Examples of such communication systems include the global system for mobile communications (GSM) (registered trademark), enhanced data rates for GSM evolution (EDGE), universal mobile telecommunications system (UMTS), wideband code division multiple access (W-CDMA), and long term evolution (LTE). The frequency bands are defined by telecommunications standards in the respective communication systems. For example, only a 2 GHz band was initially used as a frequency band in the third generation mobile communication system, but an 800 MHz band and a 1.7 GHz band were later added due to the rapid increase in the number of users. Taking convenience when overseas into consideration, it is desirable for mobile communication terminals to support an even greater number of communication systems and frequency bands. In light of these circumstances, a power amplification module for use in a multi-mode multi-band mobile communication terminal is proposed in Japanese Unexamined Patent Application Publication No. 2015-156687. The power amplification module includes a plurality of power amplifiers and a plurality of switches used to select a combination of power amplifiers that will operate in parallel in accordance with one communication system selected from among a plurality of communication systems and in accordance with the transmission power.
However, when a plurality of power amplifiers are made to operate by being connected in parallel with each other, a phase difference (phase advancement or phase retardation) may be generated between output signals of the plurality of power amplifiers due to external environmental factors such as variations between circuits operating in parallel, temperature changes, load variations and so on, and consequently oscillations may occur.